<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Timer</title>
</head>
<body>
  <input type="button" value="click" class="click">
  <input type="button" value="clear" class="clear">
  <script>
    var timer;
    document.querySelector('input.click').addEventListener('click', function(){
      timer=setInterval(function(){console.log('vvv')}, 0);
    }, false);
    document.querySelector('input.clear').addEventListener('click', function(){
      clearInterval(timer);
    }, false);
  </script>
</body>
</html>